mysql - SQLException: 找不到合适的驱动程序

Question

我有一个 Java 类，它通过我在 Tomcat 上运行的 JSP 中使用的 JDBC 访问 MySQL 数据库，但我得到了 No Driver Found Exception。

我有一个方法：

private static Statement makeStatement() {
   try{
    com.mysql.jdbc.Driver d = null;
    try{d = new com.mysql.jdbc.Driver();}catch(Exception e){
      System.out.println("ERROR BY NEW DRIVER " + e.toString() + 
      "\n");e.printStackTrace();}
    Connection con = DriverManager.getConnection(url, user, password);
    return con.createStatement();
   }catch(java.sql.SQLException ex){
      System.out.println("ERROR IN makeStatement " + "\nERROR - " +
      ex.toString() +  "\n ERROR CODE:\n " + ex.getErrorCode() + 
      "\nSQLSTATE:\n " + ex.getSQLStat        e());ex.printStackTrace();}
    return null;
 }

这会引发一个错误，Connection con = DriverManager.getConnection(url, user, password);这是我从 catalina.out 打印出来的：

  Received Parameters

ERROR IN makeStatement 
ERROR - java.sql.SQLException: No suitable driver found for 
 ERROR CODE:
 0
SQLSTATE:
 08001
java.sql.SQLException: No suitable driver found for 
        at java.sql.DriverManager.getConnection(DriverManager.java:602)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at message.Message.makeStatement(Message.java:72)
        at message.Message.query(Message.java:79)
        at message.Message.getName(Message.java:225)
        at org.apache.jsp.message_jsp._jspService(message_jsp.java:288)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:548)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
        at java.lang.Thread.run(Thread.java:619)
ERROR IN QUERY java.lang.NullPointerException
ERROR in getName java.lang.NullPointerException
-----------------------------------

  Received Parameters

        newMessage      =  
        newpassword     = 
        verifypassword  = 
        sendinfo        = 
        username        = Eli
        newusername     = 
        login   = login
        password        = tree
ERROR IN makeStatement 
ERROR - java.sql.SQLException: No suitable driver found for 
 ERROR CODE:
 0
SQLSTATE:
 08001
java.sql.SQLException: No suitable driver found for 
        at java.sql.DriverManager.getConnection(DriverManager.java:602)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at message.Message.makeStatement(Message.java:72)
        at message.Message.query(Message.java:79)
        at message.Message.validUser(Message.java:195)
        at org.apache.jsp.message_jsp._jspService(message_jsp.java:123)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:548)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
        at java.lang.Thread.run(Thread.java:619)
ERROR IN QUERY java.lang.NullPointerException
ERROR in validUser java.lang.NullPointerException
ERROR IN makeStatement 
ERROR - java.sql.SQLException: No suitable driver found for 
 ERROR CODE:
 0
SQLSTATE:
 08001
java.sql.SQLException: No suitable driver found for 
        at java.sql.DriverManager.getConnection(DriverManager.java:602)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at message.Message.makeStatement(Message.java:72)
        at message.Message.query(Message.java:79)
        at message.Message.getName(Message.java:225)
        at org.apache.jsp.message_jsp._jspService(message_jsp.java:288)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:548)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
        at java.lang.Thread.run(Thread.java:619)
ERROR IN QUERY java.lang.NullPointerException
ERROR in getName java.lang.NullPointerException

唯一重要的错误是其中一个错误，makeStatement()因为失败会导致所有其他错误。我已经四次检查我的 WEB-INF/lib 目录中是否有正确的 jar 文件，并且我重新启动 Tomcat 的次数比我想要的要多。我有一个单独的 webapp，它makeStatement()在不同的 .java 文件中使用，并且该 webapp 运行良好。更奇怪的是我在.java中有这个：

static {
  System.err.println("\n\nTEST MYSQL ACCESS: dump all relevant tables:");
  dump();
  System.err.println("END OF MYSQL ACCESS ACCESS.");
}

 public static void dump() {
   try {
     readUsers();
     for (UserRecord u: users)
     System.err.println(u.username+" "+u.password);
   } catch (Exception e) {System.err.println(e);}
 }

wherereadUsers()使用 . 从数据库中读取所有用户makeStatement()。这实际上有效，并且打印了数据库中的所有用户（出于明显的原因，此处未显示:)），然后发生未找到驱动程序错误。

Answer 1

java.sql.SQLException：找不到合适的驱动程序

此异常可能有 2 个原因：

1. 根本没有加载 JDBC 驱动程序。
2. URL 不匹配任何加载的 JDBC 驱动程序。

由于驱动程序似乎已加载（尽管方式不正确），因此 URL 看起来是完全错误的。确保url变量的值符合以下格式

jdbc:mysql://localhost:3306/dbname

也可以看看：

• 将 Java 连接到 MySQL 数据库

---

与具体问题无关：Java 代码不属于 JSP 文件。也为此努力。您的异常处理也很糟糕，您应该抛出异常（以便它阻止执行代码的剩余部分）而不是打印消息/跟踪，然后继续执行代码。

Answer 2

我必须从 WEB-INF/lib中删除mysql-connector-java-*.jar 并将其添加到 tomcat6/lib 文件夹中。（tomcat6 是安装 tomcat 的地方。）我不知道为什么这样做，但它对我有用。

Answer 3

你在司机那里注册了你的课程吗？例如：

Class.forName("net.sourceforge.jtds.jdbc.Driver");
DriverManager.getConnection(url,user,password);

Answer 4

您是否将一个空的 url 字符串传递给 getConnection()？错误消息开始

No suitable driver found for ERROR

没有找到适合 [空白] 的驱动程序？好像你没有在这里传递一个网址。

Answer 5

转到项目的库文件夹并右键单击它，然后转到“添加库”选项。现在添加 mysql.jdbc.Driver